It is common practice in many industries to use driers, ovens, kilns, etc., as part of the manufacturing operation. For example, driers are commonly used in the textile industry for the heat processing of fabrics and are used in the food processing industry for the spray drying of edible materials. As another example, in the pulp and paper industry, it is common practice to employ driers in connection with paper manufacturing machinery. Metal fabrication operations frequently employ a paint drying oven wherein hot air is used to dry the paint and remove solvents. Driers are used for drying pills and powders in the pharmaceutical industry in the calcining of gypsum, cement and ceramics, and in the curing of plastics and chemicals, etc.
In all of these processes there is a significant loss to the manufacturing operation due to the cost of heating air which is ultimately exhausted to the atmosphere.